Delay detonators for priming devices



Jan. 28, 1964 A. R. PISSACROIA 3,119,338

DELAY DETONATORS FOR PRIMING DEVICES Filed July 22. 1960 INVENTOR.ANGELO R, PISSHCRO/A WMMZZ M W United States Patent DELAY DETONATORS FORPRIMING DEVItIES Angelo Rali'aeie Pissacroia, Colleferro, Italy,assignor to Bomhrini Parodi-Delfino Societa per Azioni, Rome,

Italy, a company of Italy Filed July 22, 1960, Ser. No. 44,797 Claimspriority, application Italy Oct. 13, 1959 2 Claims. (Cl. 102-ss Thepresent invention relates to an improvement in delay detonators forpriming devices.

It is known that these delay detonators are an essential component ofthe fuses for those particular types of ammunition where it is requiredthat the explosion will occur after a pre-established time after theprojectile has struck its target.

It is known that the common delay detonators use labyrinth paths tendingexclusively to increase the transmission time of the explosive wave orparticular mixtures having a slowed down detonation speed.

According to the present invention, on the contrary, a thermo-chemicalphenomenon is exploited, which involves the projection of incandescentresidues of the combustion of the sensitive priming capsule incombination with the complementary action due to the eifect of the flameacting through restricting orifices and the speed of which is adjustedby outer vent holes.

The range of variation of the delays which may be obtained by thedetonator according to this invention, which although it is structurallya single type is capable of giving different performances with only achange of certain explosive or dimensional compositions, range from aminimum delay on the order of the ten-thousandth of one second up tovalues reaching 6 hundreds of a second.

Therefore the improvement of the present invention provides a detonatorwhich has a constant delay time, even if the thickness and materialforming the target changes, and even for changes of the impact speed ofthe fuse within the full range of the speed of the projectile.

Another object achieved by this invention is a minimum size of thedetonator within limits which heretofore were not obtainable andparticularly a detonator having a diameter of about 4 mm. and which is12 mm. long or less; therefore this detonator can be used in ammunitionof many sizes and calibers.

A further advantage offered by this invention is that the delay timewill not change during storage because stable and non-corrosiveexplosives can be used.

The improvement according to this invention will be further described inone preferred embodiment with reference to the single figure herewithattached showing an axial cross-sectional view of the device.

With reference to the drawing, the device comprises an igniting capsule1, contained in the hollow substantially cylindrical body of thedetonator proper. Said igniting capsule contains the styphnate primingmixture 3 which is impact sensitive and the capsule is provided with twoholes 4 and 4' in register with a central aperture 5 in the fore end ofthe body 2. Between the priming mixture 3 and the anvil 6 whereon reststhe mixture is located the paper seal disc 7. The anvil 6 is made ofsteel and is provided with the transmission holes 8 and 8 which areinclined to the longitudinal axis of the cylindrical body and which eachconsists of two portions, the portions 8 and 8' having a larger diameterand the portions 14 and 14 having a smaller diameter, the portions 14and 14 being toward the expansionchamber 13.

Also within the body 2 of the detonator which for instance may be madeof tinned brass, is contained the temperature sensitive styphnatetransmission charge 9, as well as the detonating explosive charge 10. Onthe end of the charge 10 is applied a tetryl booster explosive charge 11which is surrounded by the closure member 12.

The feature of the device which has been thus briefly described in itscomponent parts, resides in that instead of relying upon the explosiveWave of the priming charge 3, the detonation brought about by thecombination of the thermal effect of the action of the gas whichcontacts the igniting surface of the detonator charge 9 and of themechanical and thermal effect due to the projection of incandescentresidues from the combustion of the charge 3, through the two holes 8and 8' against the heat sensitive mixture 9.

The delay time is mainly a function of the outlet speed of the burnedgas from the capsule 3 and of the impact energy of the solid residuesfrom said'capsule which are produced at the moment when it is ignited.

The control of the pressures due to the priming action of the sensitivemixture 9 of the igniting capsule, in the restricted room afforded bythe expansion chamber 13 overlying the detonating mixture proper 919 isobtained, according to this invention, by causing on one hand aremarkable decrease of the pressure by venting the products of theprimer combustion through the holes 4 and 4' provided in the flatsurface of the capsule and providing a restricting action on the passageof the gas from the larger diameter duct portions 8 and 8' into smallerdiameter duct portions as shown at 14 and 14".

In the dynamics of the sequence of the ignition phenomena, particularfeatures are required for the detonating mixture 9li0 compressed in thedetonator proper. According to this invention said mixture must be suchthat in the first portion 9 exposed to the combustion products from thecapsule 3, through the ducts the priming feature due to the temperatureeffect will be enhanced, while both sensitivities due to attrition andexplosive wave effects are small. Further, in case of longer delays, thevariation of the deflagration speed of the initial status of thedetonating charge as a function of the variation of the pressure shouldbe a minimum, so that in correct combination with the features adoptedfor the capsule, for these values of delay, the results will also bevery constant.

The efiect of decreasing the diameter of the portion 14 and 14' of theducts which are closer to the expansion chamber is that this reduceddiameter acts as a choke to reduce the time in which sufiicient gaseswill pass through the duct to ignite the thermally sensitive explosive9. Reference to any standard handbook will show that the weight of a gasdischarged from an orifice is proportional to the coefiicient ofdischarge of the orifice, the area of the orifice and the pressure ofthe gas. Where other conditions are the same, the weight discharged willbe proportional to the area. It is the weight of gas which isdeterminative of the time at which the thermally sensitive explosive 9will be ignited. This is because it takes a given amount of heat toignite this explosive, which given amount of heat will be conveyed by agiven amount of gases from the explosive primer 3. Since the primer 3remains the same, the pressure upstream of the duct portions 14 and 14'will be generally the same, so that reducing the area of the orificeswill reduce the amount of gas discharged therethrough. This of course isthe amount discharged per unit of time, so that in order to discharge asufficient amount to ignite the thermally sensitive explosive 9, thesmaller the area of the duct portions 14 and 14', the longer the time todischarge the required amount of gas. Thus the relative amounts of gaspassing through the ducts and the orifices can be controlled by therelative sizes of the ducts and the orifices to control the delay timeof the detonator.

The present invention has been illustrated and described in onepreferred embodiment, it being understood however that constructivechanges may be practically adopted without departing from the scope ofthe appended claims.

I claim:

1. A delay detonator for priming devices, consisting essentially of ahollow cylindrical body open at the rear end and provided with a centralaperture at the fore end, an igniting capsule located in the fore partof the hollow body and just inside the said central aperture, saidignit-v ing capsule having a priming mixture therein, an explosivemixture contained in the rear part of the hollow body, said ignitingcapsule and said explosive mixture being spaced along the hollow body toleave an expansion chamber between them, said igniting capsule havingthe end facing said aperture provided with holes in register with thesaid central aperture of the hollow body, and an anvil located in thefore part of the hollow body between the igniting capsule and saidexplosive mixture and extending into the said igniting capsule on theopposite end to the end having said holes therein and abutting saidpriming mixture, said anvil having holes between said igniting capsuleand the said expansion chamber inclined to the longitudinal axis of saidcylindrical body and connecting said igniting capsule with saidexpansion chamber, said inclined holes each consisting of two portions,one having a larger diameter and the other having a smaller diameterwith the portion on the end toward the expansion chamber having thesmaller diameter for enabling control of the speed of the flow of thegas generated by the priming mixture through said inclined holes intothe expansion chamber, whereby when said priming mixture is ignited itdischarges a portion of the gases generated by the priming mixture intothe atmosphere through said holes made in the end of the ignitingcapsule facing said aperture and said central bore and conveys theremaining gas toward the expansion chamber through said inclined holesand the relative amounts of gas can be controlled by the relative sizesof the holes in the capsule and said inclined holes.

2. A delay detonator as claimed in claim 1, in which the said explosivemixture contained in the rear part of the hollow body comprises a frontportion of an explosive sensitive to the thermal action of the gasescoming from the priming mixture and to the thermal-mechanical action dueto the projection of the incandescent residues from the said primingmixture, and a detonating rear portion, there being further provided abooster charge adjacent to the said detonating portion and a capcontaining said booster charge and closing the rear end of the hollowbody.

References Cited in the file of this patent UNITED STATES PATENTS547,852 Hathaway Oct. 15, 1895 953,850 Loeble Apr. 15, 1910 1,313,801Doran Aug. 19, 1919 1,821,608 Babbit Sept. 1, 1931 2,381,900 Graumann etal. Aug. 14, 1945 2,912,934 Baker Nov. 17, 1959 2,926,607 Muller Mar. 1,1960 FOREIGN PATENTS 20,467 Great Britain 1902 251,874 Great Britain May13, 1926 286,137 Italy June 2, 193]

1. A DELAY DETONATOR FOR PRIMING DEVICES, CONSISTING ESSENTIALLY OF AHOLLOW CYLINDRICAL BODY OPEN AT THE REAR END AND PROVIDED WITH A CENTRALAPERTURE AT THE FORE END, AN IGNITING CAPSULE LOCATED IN THE FORE PARTOF THE HOLLOW BODY AND JUST INSIDE THE SAID CENTRAL APERTURE, SAIDIGNITING CAPSULE HAVING A PRIMING MIXTURE THEREIN, AND EXPLOSIVE MIXTURECONTAINED IN THE REAR PART OF THE HOLLOW BODY, SAID IGNITING CAPSULE ANDSAID EXPLOSIVE MIXTURE BEING SPACED ALONG THE HOLLOW BODY TO LEAVE ANEXPANSION CHAMBER BETWEEN THEM, SAID IGNITING CAPSULE HAVING THE ENDFACING SAID APERTURE PROVIDED WITH HOLES IN REGISTER WITH THE SAIDCENTRAL APERTURE OF THE HOLLOW BODY, AND AN ANVIL LOCATED IN THE FOREPART OF THE HOLLOW BODY BETWEEN THE IGNITING CAPSULE AND SAID EXPLOSIVEMIXTURE AND EXTENDING INTO THE SAID IGNITING CAPSULE ON THE OPPOSITE ENDTO THE END HAVING SAID HOLES THEREIN AND ABUTTING SAID PRIMING MIXTURE,SAID ANVIL HAVING HOLES BETWEEN SAID IGNITING CAPSULE AND THE SAIDEXPANSION CHAMBER INCLINED